JPH05272933A - Method for solder visual inspection - Google Patents

Abstract

PURPOSE:To obtain the method which can excellently measure the shape of solder. CONSTITUTION:A starting position S of laser light L is set at the central part C of an upper surface 2a of a lead. The laser light L is made to scan in the direction N1 directed toward the side of a light receiving part 6 from a laser emitting device 5. The edge E of the lead 2 on the side of the light receiving part 6 is detected. An offset point B is set between the edge E and the center A of the lead 2. The laser light L is made to scan in the direction N2 of the length of the lead 2 passing the offset point B. Thus, the shape of solder 3, which is bonded to the tip part of the lead 2, is measured. The laser light is not cast in the vicinity of the edge of the lead 2 at the opposite side of the light receiving part. The secondary reflection from a neighboring lead is avoided. Thus, the edge at the side of the light receiving part to be obtained can be readily detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder visual inspection method for adhering a lead of an electronic component to a substrate, in which the shape of the solder is measured while satisfactorily reflecting laser light to the light receiving portion side. Is.

[0002]

2. Description of the Related Art After the leads of an electronic component such as an IC, an LSI or a TAB chip are attached to a substrate by soldering,
A visual inspection of the solder is performed to determine the quality of the soldered state.

FIG. 8 shows a conventional appearance inspection means using a laser beam. In the figure, 1 is a main body of electronic parts, and 2,
Reference numeral 2'denotes a lead extending from the main body 1, 3 a solder for bonding the lead 2 onto the circuit pattern 7 of the substrate 4, 5 a laser irradiator, and 6 a light receiving portion.

This conventional method is performed as follows. First, the laser light L is scanned so that the laser light L completely traverses from the edge E ′ on the opposite side of the light receiving portion 6 of the lead 2 to the edge E on the light receiving portion 6 side (direction N1).
Then, the reflected light L ′ is received by the light receiving portion 6 to obtain the center A of the lead 2.

Next, the laser light L is scanned in the length direction N2 of the lead 2 passing through the center A, and the reflected light L'is received by the light receiving portion 6, whereby the solder 3 along the direction N2 is received. The shape is measured, and the quality of the shape of the solder 3 is determined based on the result.

[0006]

The lead 2 has a generally semicylindrical cross section, and the upper surface 2a thereof is curved in an arch shape. Moreover, the curvature is not always constant, and the shape of the upper surface 2a varies depending on each lead.

Therefore, in the above conventional means, when the laser light L is scanned in the N1 direction, the laser light radiated particularly near the edge E'of the lead 2 on the side opposite to the light receiving portion 6 is indicated by an arrow a. 2 on adjacent lead 2 ', as shown in
It is likely that the secondary reflection light a is secondarily reflected and is incident on the light receiving unit 6. Therefore, as shown in FIG. 9, the curved line showing the measured value largely fluctuates to form a large number of uneven portions, and which convex portion integrally shows the edge E on the side of the light receiving unit 6 depending on only this curved line. In many cases, it is difficult to make a sudden judgment. This means that the position of the edge E is obtained without using human hands by using a computer, and the lead 2 is scanned in the longitudinal direction on the basis of the edge E to cause a large neck in the automatic visual inspection of the solder. It will be.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional means and to provide a method capable of satisfactorily measuring the shape of solder.

[0009]

To this end, the present invention provides a laser irradiator for irradiating a laser beam from above toward a lead extending from a main body, and a reflected light from this lead obliquely above the lead. A light receiving section for receiving light is used to inspect the appearance of the solder, and the start position of the laser beam is set at the center of the upper surface of the lead, and the laser beam is transmitted from the laser irradiator to the light receiving section side. The process of scanning in the direction to detect the edge of the lead on the light receiving side, the process of setting an offset point between this edge and the center of the lead, and the length of the lead passing through the offset point A process for scanning the laser beam in the direction to measure the shape of the solder adhered to the tip of the lead is constituted.

[0010]

According to the above construction, the laser light is not irradiated near the edge of the lead on the side opposite to the light receiving portion, the secondary reflection can be avoided, and the fluttering of the measured value can be reduced. ..

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 shows a solder visual inspection means according to the present invention. The configuration is almost the same as the conventional means shown in FIG. 8, and the description of the configuration is omitted by giving the same reference numerals. In the present means, the laser irradiator 5 is arranged so that the laser light L can be emitted toward the lead 2 from vertically above, and the reflected light L ′ from this lead 2 is received obliquely above the lead 2. The light receiving unit 6 is provided.

First, the central portion C of the upper surface 2a of the lead 2
The start position S of the laser light L is set to (see a partially enlarged view of FIG. 1). The start position S can be set appropriately in the central portion C, but the adjacent lead 2 '
In order to surely prevent the secondary reflection due to, it is desirable to set it on the light receiving portion 6 side with respect to the center A. Since the start position S is set in the central portion C in this way, as shown in FIG. 2, from the set start position S (see the solid line) to the position S'when actually measuring (see the chain line). ) Is slightly shifted to the opposite side of the light receiving section 6 (direction of arrow N3), the laser light L is not irradiated near the edge E'on the opposite side of the light receiving section 6. Moreover, since the laser irradiator 5 irradiates the lead 2 with the laser light L from vertically above, there is almost no possibility that the laser light L is secondarily reflected by the adjacent lead 2'and enters the light receiving portion 6. Absent.

Next, the laser light L is scanned in the direction from the laser irradiator 5 to the light receiving portion 6 side (direction of arrow N1). That is, the laser light L passes through the edge E from the start position S and leaves the lead 2. Figure 3 (a) shows
It is an example of a graph of measured values obtained by this scanning. In FIG. 3A, P indicates the end point of scanning. In this graph, the center of the start point S and the end point P is set to the position of the edge E.

Now, even if the edge E'on the opposite side of the light receiving portion 6 is excluded from scanning and the secondary reflection from the adjacent lead 2'is avoided, the measurement is performed as illustrated in FIG. 3 (a). The values often have irregularities. Next, FIG. 3 (b)
~ (C), referring to FIG. 4, FIG. 5, and FIG.
A process of detecting the edge E on the side of the light receiving unit 6 will be described. First, the measured value is smoothed by the moving average method (step 4 in FIG. 7) to obtain a smooth curve with fine irregularities removed (FIG. 3 (b)). Next, the convex points (Δ in FIG. 3C) and concave points (∇ in FIG. 3C) of this curve are extracted (step 5 in FIG. 7). These convex and concave points can be obtained by simple calculation, but in order to fit the number of convex and concave points to an appropriate number, when a certain point is to be calculated, several points before and after that point Should be included in the calculation, and should be calculated while averaging the gradient to some extent. If there is a convex point next to the start position S, the start point S
Is a concave point, and when there is a convex point immediately before the end point P, the end point P is a concave point. Here, in FIG. 3C, D1,
D2 and D3 are concave points, and U1, U2, U3 and U4 are convex points.

Any one of the convex points U1, U2, U3 and U4 is a convex point indicating the position of the edge E. next,
An advantageous means for automatically determining which of these convex points indicates the edge E using a computer will be described. This means uses a plurality of parameters H (i), X as shown in steps 6 to 11 of FIG.
(I), Y (i), Z (i) are calculated, and their sum S
(I) is calculated and an evaluation score table (Fig. 5) is created, and the evaluation score S
By (i), it is determined which of the convex points U1, U2, U3 and U4 is the convex point for the edge E.

Height parameter H in step 6 of FIG.
As shown in FIG. 4A, the reference line B. L.
Convex points U1, U from (for example, the horizontal axis of the graph of measured values)
2, the heights H1, H2, H3, H4 of U3, U4 and the height H of the edge E of the chip data (known) of the lead 2 are compared, and the one closest to the height H of the edge E is obtained. .. Specifically, H (i) = (| H−Hi | / H) × K1 (where K1 is a weighting coefficient, i = 1, 2, 3, 4) is calculated, and H (i) is minimum. If so, it is evaluated as having a high probability of being a convex point to be obtained.

Similarly, as shown in FIG. 4B, the position parameter X (i) in step 7 of FIG. L. (When the start position S and the end point P are set as described above, the edge E is located on this line SL)
1, Distance to U2, U3, U4 X1, X2, X3, X
4, X (i) = Xi × K2 (K2 is a weighting coefficient, i = 1, 2, 3, 4). If X (i) is the smallest, the above probability is evaluated as high.

The drop parameter Y (i) for the next concave point in step 8 of FIG. 7 is the distance Y of FIG. 4 (c).
1, Y2, Y3 are obtained and Y (i) = (| H−Yi | / H) × K3 (where K3 is a weighting coefficient, i = 1, 2, 3).

Further, in step 9 of FIG. 7, the drop parameter Z (i) for the immediately preceding concave point is obtained by calculating the respective distances Z1, Z2, Z3, Z4 of FIG. 4 (d), and Z (i) = (Zi / H) × K4 (where K4 is a weighting coefficient, i = 1, 2, 3, 4). If the above parameters Y (i) and Z (i) are also minimum, the above probability is evaluated as high.

Then, in step 10 of FIG. 7, the evaluation points S (i) = H (i) + X (i) + Y (i) + Z.
(I) is calculated, and the convex point having the smallest evaluation point S (i) is set as the convex point (decision point) corresponding to the edge E (step 12 in FIG. 7). It should be noted that some of these parameters may be omitted, and convenience weighting factors K1, K2, K3, K may be omitted.
4 may be changed.

Next, an offset point B is set between the edge E (determination point) and the center A of the lead 2 (FIG. 7).
Step 13). The width of the lead 2 is included in the chip data and is known, and the offset point B can be easily set.

In FIG. 9 (a graph of measured values by the conventional means), K indicates the abnormal reflection of the laser light by the edge E'on the side opposite to the light receiving portion 6, and this abnormal reflection causes the lead 2 to move. It is difficult to find the center A accurately,
As described in the section of the problem to be solved by the invention.

Next, as shown in FIG. 1, the laser light L is scanned in the length direction N2 of the lead 2 passing through the offset point B, and the reflected light L'is received by the light receiving portion 6, The shape of the solder at the tip of the lead 2 is measured (step 14 in FIG. 7).

FIG. 6 shows the lengthwise shape N2 of the lead 2 measured in this way, in which 20 is the top surface shape of the lead 2 and 30 is the top surface shape of the solder 3. Yes, the quality of the shape of the solder 3 is judged from the top surface shape 30.

As described above, according to the present method, it is possible to avoid the deviation of the measurement value due to the secondary reflection of the laser light by the edge E'on the opposite side of the light receiving section 6 and to easily find the position of the edge E. In addition, the position of the edge E can be detected by a manual inspection using a computer, and automation of the visual inspection of the solder can be promoted.

[0027]

According to the present invention, a laser irradiator for irradiating a laser beam from above toward a lead extending from a main body and a light receiving portion for receiving reflected light from the lead obliquely above the lead are used for soldering. Of inspecting the appearance of, the start position of the laser beam is set in the central portion of the upper surface of the lead, and the laser beam is scanned in the direction from the laser irradiator to the light receiving unit side, The process of detecting the edge of the lead on the side of the light receiving portion, the process of setting an offset point between this edge and the center of the lead, and scanning the laser light in the length direction of the lead passing through the offset point. The process for measuring the shape of the solder adhered to the tip of the lead is configured so that the laser light is not emitted near the edge of the lead on the side opposite to the light receiving part. To avoid secondary reflection by adjacent leads, it is possible to easily detect the light receiving portion side of the edge to be obtained. Further, the shape of the solder can be satisfactorily measured by scanning the laser light along the length direction of the lead and surely reflecting the reflected light to the light receiving portion side.

[Brief description of drawings]

FIG. 1 is a perspective view of a visual inspection means according to an embodiment of the present invention.

FIG. 2 is a sectional view according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a measurement example according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram of parameters according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of evaluation points according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram of a measurement example according to an embodiment of the present invention.

FIG. 7 is a flowchart according to an embodiment of the present invention.

FIG. 8 is an explanatory view of conventional means.

FIG. 9 is an explanatory diagram of a measurement example of conventional means.

[Explanation of symbols]

 1 main body 2 lead 2a lead upper surface 2'lead 3 solder 5 laser irradiator 6 light receiving part A lead center B offset point C center part E light receiving side edge L laser light L'reflected light N1 direction toward light receiving side N2 Lead length direction S Start position

Claims (1)

[Claims] 1. A solder irradiator for irradiating a laser beam from above toward a lead extending from a main body and a light receiving section for receiving reflected light from this lead obliquely above the lead, thereby improving the appearance of the solder. What is inspected, the start position of the laser beam is set in the center of the upper surface of the lead,
The process of scanning the laser beam in the direction from the laser irradiator to the light receiving portion side to detect the edge of the lead on the light receiving portion side, and an offset point between the edge and the center of the lead. Solder characterized by comprising a setting process and a process of scanning the laser light in the length direction of the lead passing through the offset point to measure the shape of the solder bonded to the tip of the lead. Appearance inspection method.